Momentary switches are commonly used for turning on and off electrical and electronic equipment. They operate in combination with a switch circuit located on a microcontroller to produce a logic type operation so that when a switch pulse is supplied to a switch circuit, the circuit switches from “off” to “on” or from “on” to “off”. The switch pulse is provided by actuation of the momentary switch which when actuated completes the circuit to provide a pulse to the switch circuit to switch the state of the switch circuit.
It is common practice for a number of different types of electrical and electronic equipment to use only a single momentary switch to switch the equipment both on and off.
However, one of the disadvantages of using a single momentary switch is that, during the off state, it is still necessary for power to be supplied to the switch circuit. This is because it is necessary to maintain a live switch circuit for sensing a switch pulse generated by the momentary switch at any time. Therefore, this power consumption constantly drains the battery or AC power even though the electronic equipment appears to be in an “off” state to a user. This consumption of electrical power is especially important to battery operated equipment such as laptop computers and mobile (or hand) phones where a long battery life is preferable in order to cut down on the need to constantly change or recharge batteries.